The present invention relates to variable area nozzles of the type employed with either a turbine or compressor rotor and more particularly to a nozzle assembly including intermeshing gear segments for positively positioning nozzle vanes.
Variable area nozzles are utilized in gas turbine engines to improve efficiency over relatively wide ranges of operating rotor speeds. In such nozzles, it is necessary to accurately position each of the movable vanes and to maintain them in selected positions during the operation of the turbine rotor. Such accuracy is difficult to maintain, for example, due to excessive tolerances arising in a drive arrangement for positioning the vanes, to distortion caused by the flow of hot gases through the nozzles, and to distortion caused by imbalanced loading on the actuator parts.
In the prior art, one arrangement for controlling movable nozzle vanes employs a ring gear arranged about the nozzle vanes for simultaneous positioning thereof. Exemplary of such prior art systems are those disclosed in U.S. Pat. Nos. 3,252,686 to Chadwick; 3,383,090 to McLean; and 3,376,018 to Williamson. Each of these arrangements utilize single actuator jacks for rotating a ring member which causes the simultaneous actuation of a plurality of vanes through connecting means. Such systems, due to the single point force application from the actuator jack, cause an imbalance of loading on the ring member which can lead to distortion of the parts and inaccuracy in nozzle placement.
Other prior art devices utilize a plurality of separate actuator jacks connected to various points along a ring gear to position same. Again, an imbalance of forces on the ring gear is occasioned by any unequal or imprecise movement of the multiple jacks.
The present invention is directed to a simple and inexpensive nozzle actuator system which produces balanced forces on the operable components and which produces accurate and precise simultaneous positioning of a plurality of nozzle vanes.